This invention relates to centrifuges and more particularly to swinging bucket type centrifuges.
Swinging bucket centrifuges typically include a rotor having a pluralilty of peripheral cavities therein. Each cavity houses a swinging member, usually referred to as a bucket, which holds the material to be centrifuged. The buckets are pivotally mounted in each cavity, such that they normally hang with a vertical orientation. As the rotor increases speed, the buckets, because of centrifugal force, swing outwardly and desirably assume a horizontal position. The pivotal mounting is provided with some means of flexure by which the buckets, under the influence of extreme centrifugal force at the higher speeds of rotation, are permitted to move radially outward until they are supported by or seated within the rotor cavity itself such that they are restrained from further outward movement. The reverse sequence occurs as the rotor is slowed down, i.e., the buckets are retracted radially inward such that they unseat from the rotor cavity and are allowed to swing back down to a vertical orientation.
Among the early designs of these type of rotors, flexure was provided by elongated pins which extended through a section of the rotor. Unfortunately these pins required a relatively large amount of rotor space and severely limited the number of cavities and, hence, the number of buckets that could be positioned within one rotor.
An improvement over this design which permitted the use of more swinging buckets in a given rotor was provided by Galasso et al. in U. S. Pat. No. 3,393,864, issued July 23, 1968. Galasso et al. taught that each of the buckets is supported by an independent bucket hanger assembly disposed with a cavity in the rotor. Each hanger assembly is spring biased in a radial direction towards the axis of rotation of the rotor and includes a separate pin member carried by the assembly from which a bucket can be suspended. While the Galasso et al. apparatus provided a vast improvement over the pin mountings, it unfortunately has many disadvantages. Among these disadvantages is that the hanger mounting screws can and do become loosened with use and vibration. In this event, the required precise positioning of that bucket is lost. The bucket hanger can then rotate which may cause the bucket to drop off or not seat properly. Either can result in an unbalanced rotor and cause possible rotor spin-off at high speed. The resulting damage can be very expensive.
Another swinging bucket rotor is described by Chulay, in U.S. Pat. No. 3,752,390, issued Aug. 14, 1973. In Chulay, the rotor cavities each have a vertically positioned torsion bar extending downwardly through the rotor into the bucket cavity. A disadvantage of the Chulay assembly, as well as the Galasso et al. assembly, is that the bucket, which must be precisely mounted, can easily be mounted backwards by the careless user. This can result in rotor imbalance. Further the buckets can be improperly mounted such that they are not securely engaged by the hook support provided. In this case, the buckets may fly off as soon as the rotor begins operation.
Accordingly, it is an object of this invention to obviate many of the difficulties encountered in the prior art swinging bucket type centrifuges.
A further object of this invention is to provide a centrifuge rotor which has an improved bucket hanger assembly.
An additional object of this invention is to provide an improved swinging bucket centrifuge which facilitates the proper positioning of the buckets.